Too much to even count but I'll try to list them.
Rose McIver - Once Upon A Time
David Anders - Once Upon A Time, Criminal Minds
Bradley James - Merlin
Drew Ray Taylor - Riverdale
Jane Lynch (Cameo) - Criminal Minds, Glee
Robert Knepper - Criminal Minds
Molly Hagen - No Good Nick (I think?)
Eddie Jemison - Veronica Mars (Movie), Criminal Minds, NCIS
Hiro Kanagawa - Criminal Minds
Raphael Sbarge - Once Upon A Time, Criminal Minds, Grey's Anatomy
Robert Ri'chard - Veronica Mars, NCIS, Lucifer
Ryan Hansen - Veronica Mars
Percy Daggs III - Veronica Mars
Francis Capra - Veronica Mars, Criminal Minds
Enrico Colantoni - Veronica Mars
Kristen Bell (Cameo) - Veronica Mars, The Good Place, Frozen I
Jason Dohring - Veronica Mars
Daran Norris - Veronica Mars
Ken Marino - Veronica Mars
Chris Lowell - Veronica Mars, Grey's Anatomy, Private Practice
Adam Rose - Veronica Mars
Rob Thomas (I know he ain't an actor but he was mentioned in VM)
I think that's it.
